High-power high-repetition-rate UV light at 355 nm generated by a diode-end-pumped passively Q-switched Nd:YAG laser

Abstract

We describe experimental results with a diode-pumped, passively Q-switched extracavity second- and third-harmonic generation. Cr:YAG is used as a saturable absorber for pulse generation. Taking into account the thermal effects of Nd:YAG at high incident pump power, we use a short plane-to-plane cavity configuration to take advantage of the maximum pump power and obtain the compactness structure. At the same time, we use the type-I critical phase-matched lithium triborate crystal to generate light at 532 nm and mix the residual fundamental at 1064 nm and the second-harmonic wave at 532 nm in the type-II critical phase-matched lithium triborate crystal for UV light generation at 355 nm. A third-harmonic-generation output power of 1.32 W is achieved at the incident pump power of 27.5 W, corresponding to an optical-to-optical efficiency of 4.8%. The instability of the UV laser power is less than 5% for 4 h.

Short pulse duration of a 355-nm laser by extracavity sum-frequency mixing with a LiB3O5 (LBO) crystal

“…The parameters used in our calculation are: ξ = 0.4, K c = 0.0523 W/K cm, ω p = 260 µm, n 0 = 2.183, and α T = 4.43×10 −6 /K. Due to the beam waist is located at the position of the plane mirror, the corresponding beam size can be calculated as [3]:…”

Electro-optical Q-switch low-repetition-rate narrowpulse-width UV pulse laser at 355 nm generated by pulsed-diode-pumped Nd:YAG

“…The polarization match is shown as follows: o(1064 nm) + e(1064 nm) → o(532 nm) for SHG, o(532 nm) + e(1064 nm) → e(355 nm) for THG [11].…”

Enhanced 355-nm generation using a simple method to compensate for walk-off loss

“…From the above equation, the output power ratio of the compensated sum-frequency beam with respect to uncompensated one, 3 …”

“…Then, the generated green beam and the residual IR beam are mixed to generate the UV beam. Although there are many nonlinear crystals that can be for these two processes, lithium triborate (LBO) crystals are the most common for IR lasers that have a peak power below 1 MW [1][2][3][4][5][6][7][8][9], owing to their deep UV transparency, large nonlinearity, relatively small walk-off loss, and high growth yield. The LBO crystal for the IR-to-green conversion can have noncritical phase matching (NCPM) condition, while the one used to mix the IR and green to UV cannot.…”